The invention relates to the area of allogeneic cellular vaccines. More particularly, the invention relates to the use of allogeneic cellular vaccines for the prevention and treatment of tumors, especially of the central nervous system. The invention also relates to the prevention and treatment of infectious diseases.
Brain tumors have historically proved resistant to cell mediated immunotherapies. Previously, it had been postulated that the brain is an immunologically privileged site based upon studies in which tumors transplanted into the brains of outbred rats were often successfully established, whereas the same tumors transplanted subcutaneously were frequently rejected (Shirai 1921; Murphy and Sturm 1923). Further studies demonstrated that histoincompatible skin grafts, which were vigorously rejected when applied orthotopically, grew successfully when implanted within the brain away from the ventricular system (Medawar 1948). The concept of immunologic privilege within the brain has also been supported clinically by the failure of tumors metastatic to the central nervous system (CNS) to respond to immunotherapy protocols that were successful systemically (Grooms et al. 1977; Mitchell 1989). In contrast, inflammatory cells have been observed to regularly infiltrate gliomas (Ridley and Cavanagh 1971; Takeuchi and Barnard 1976; Wood and Morantz 1979). Recent studies have demonstrated that primary subcutaneous tumor transplants can confer resistance to subsequent intracerebral tumor challenge (Scheinberg et al. 1963; Scheinberg et al. 1965; Fakhrai et al. 1996; Sampson et al. 1996). Thus, the more contemporary hypothesis is that the immune privilege of the brain is only partial, particularly with respect to brain tumors. That is, brain tumors express antigens that are potentially immunogenic, but the host""s immune system is unable to mediate tumor rejection.
Recently, a number of groups have transfected genes encoding a variety of proteins into brain tumor cells in an attempt to overcome the relative lack of immune response to brain tumors. Genes encoding a variety of cytokines, such as xcex3-interferon (Watanabe et al. 1989; Mizuno et al. 1994), TNF-xcex1 (Takaoka et al. 1994), and IL-7 (Aoki et al. 1992) have been transfected into brain tumor cells and have led to reduced tumor cell growth in animal models. Several investigators have cotransplanted tumor cells with cytokine-secreting cells. Co-transplantation of IL-4-secreting LT-1 plasmacytoma cells with the U87 MG human glioma line intracerbrally in athymic mice resulted in prolonged survival compared with U87 MG alone (Yu et al. 1993). Co-implantation of IL-2 and IFN-xcex3 producing allogeneic fibroblasts with G1261 glioma (Glick et al. 1995) resulted in increased survival as compared to G1261 alone. Co-implantation of RG-2 glioma cells and retrovirally infected cell lines producing IL-2 or IFN-xcex3 generated a cell-mediated anti-tumor response. However, this response was short-lived, and animals suffered severe toxicity, including vasogenic brain edema and early demise (Tjuvajev et al. 1995).
There have now been several reports of successful active immunotherapy in rodent brain tumor models using intradermal vaccines. Fakhrai et al. have reported the effects of a vaccination strategy employing a TGF-xcex2 antisense methodology in eradicating the 9L gliosarcoma from the CNS (Fakhrai et al. 1996). More recently, we have reported that subcutaneous vaccination with irradiated B16-F10 murine melanoma cells, genetically engineered to produce GM-CSF, IL-3, or IL-6, stimulated a potent and persistent response to intracerebral B16-F10 tumors and offered protection against CNS tumor challenge. Subcutaneous vaccination with irradiated B16-F10 cells producing GM-CSF also increased the survival of CNS tumor-bearing mice (Sampson et al. 1996).
A major limitation to all of these approaches is the reliability of obtaining and growing tumor cells from a high percentage of fresh tumor samples without contamination by normal tissue (Dillman et al. 1993; Logan et al. 1993). The use of autologous CNS tissue for the generation of vaccines also carries the hypothetical risk of causing an experimental allergic encephalitis-like illness if cross-reactive antigens are present in the vaccine and tolerance is broken (Strauss et al. 1982; Dal Canto et al. 1995; Swanborg 1995).
Thus, there is a need in the art for renewable, safe, cost-effective therapeutic methods for delivering antigens specific to tumors or infectious agents to the immune system of a mammal.
It is an object of the invention to provide a method of immunizing a mammal against an antigen.
It is another object of the invention to provide a method of immunizing a mammal against two or more antigens.
It is a further object of the invention to provide a method of immunizing a mammal against a disease-specific antigen.
These and other objects of the invention are provided by one or more of the embodiments described below. One embodiment of the invention provides a method of immunizing a mammal against an antigen. The mammal is immunized with an allogeneic cell which has been transfected with a recombinant nucleic acid molecule which encodes the antigen. The transfected cell expresses the antigen.
Another embodiment of the invention provides a method of immunizing a mammal against an antigen. The mammal is immunized with at least two allogeneic cells. A first allogeneic cell has been transfected with a recombinant nucleic acid molecule which encodes an antigen. The first transfected cell expresses the antigen. The second allogeneic cell has been transfected with a recombinant nucleic acid molecule which encodes a cytokine. The second transfected cell expresses the cytokine.
A further embodiment of the invention provides a method of immunizing a mammal against two or more antigens comprising the step of immunizing the mammal with an allogeneic cell which has been transfected with a recombinant nucleic acid. The nucleic acid comprises two or more open reading frames, each of which encodes an antigen. The transfected cell expresses each of the antigens.
Another embodiment of the invention provides a method of immunizing a mammal against a disease-specific antigen. The presence of a disease-specific antigen in a mammal is determined. The mammal is then immunized with an allogeneic cell which has been transfected with a recombinant nucleic acid molecule which encodes the disease-specific antigen. The allogeneic cell expresses the disease-specific antigen.
The present invention provides the art with allogeneic cellular vaccines which can induce potent CTL responses against an antigen. The invention can be used, inter alia, to prevent or treat a tumor or a disease caused by an infectious agent in a mammal.